P0304 CEL code

[hydroponik]

Well here's some background to my story.

About a month of so ago once it got really cold, my 2001 toyota solara started hesitating while trying to accelerate. On two separate occasions, the CEL would start blinking, but it never stayed on. I knew the engine was probably misfiring b/c I never changed the plugs (@ 141k miles), so I bought 6 ngk iridium plugs.

With me being lazy and busy, I kept putting off replacing the plugs, but last week the CEL blinked and stayed on this time.

I had all plugs replaced and it fixed the hesitation problem, in fact, I've even regained some lost power. But after a week of driving, the CEL still has not gone away. I went to autozone to pull codes and I got P0304, which could mean cylinder 4 is misfiring.

Why would only one cylinder be affected? I do notice when the engine is still cold, if I am in drive but stopped, I can feel the engine "hiccuping". Could it be a bad plug or maybe something with the fuel injectors?

 

[Quiksilver]

spark wires?

 

[PottedMeat]

bad coil pack?


huh, these things use 1 coil pack for 2 cylinders

http://www.rockauto.com/catalog/raframecatalog.php?carcode=1375310&parttype=7060

 

[Bartman39]

bad coil pack?


huh, these things use 1 coil pack for 2 cylinders

http://www.rockauto.com/catalog/raframecatalog.php?carcode=1375310&parttype=7060

Not sure why they are saying 3 per but those are single coil packs so would take a total of 6... I would agree on the bad coil pack and most likely it was caused by leaving those plugs in to long and it basicly killed #4`s coil pack... If you change that coil pack be sure to get a new plug for it as well even though the plugs are fairly new it takes no time for a plug to go bad with bad coil pack...

 

[Squisher]

A CEL won't go out until you've restarted the car a number of times even if the problem is fixed. You can clear it by taking off a battery cable or have someone with a OBD tester reset it. When you went to autozone did you ask them to reset it? The last time I went there this chick said she couldn't reset mine, said it was against the law. I didn't argue, I just pulled off a battery cable for a few seconds and then had to reset all my presets on my radio.

 

[Zenmervolt]

If it's not blinking anymore, it's not misfiring. It's just staying on from the stored code.

A misfire will cause the light to blink, not just come on solid, because a misfire is more serious than most other CEL issues and carries with it the potential to damage the catalytic converter comparatively quickly rather than just denoting a monitoring failure. So if the light has stopped blinking, the engine has stopped misfiring.

ZV

 

[hydroponik]

spark wires?

Doubt it was this, I remember getting these changed around the 80k mark, however I don't know why I didn't replace the plugs at the same time lol.

Not sure why they are saying 3 per but those are single coil packs so would take a total of 6... I would agree on the bad coil pack and most likely it was caused by leaving those plugs in to long and it basicly killed #4`s coil pack... If you change that coil pack be sure to get a new plug for it as well even though the plugs are fairly new it takes no time for a plug to go bad with bad coil pack...

From what I've read, these 3 coil packs control 2 cylinders each. Thankfully they're in the front so if these are the problem, I can easily change them in this weather. I don't want to go down this route if I don't have to as they are still pretty expensive and I'm planning to buy a new car this spring or summer. Is there anyway to check if it's really bad or if there is another issue?

A CEL won't go out until you've restarted the car a number of times even if the problem is fixed. You can clear it by taking off a battery cable or have someone with a OBD tester reset it. When you went to autozone did you ask them to reset it? The last time I went there this chick said she couldn't reset mine, said it was against the law. I didn't argue, I just pulled off a battery cable for a few seconds and then had to reset all my presets on my radio.

Yes, I believe it's after 3 or so "cycles" if the ecu doesn't detect the same issue. The autozone dude wouldn't reset the code, and I just haven't had a chance to remove the battery. I'll try this weekend and see if CEL comes back.

 

[hydroponik]

If it's not blinking anymore, it's not misfiring. It's just staying on from the stored code.

A misfire will cause the light to blink, not just come on solid, because a misfire is more serious than most other CEL issues and carries with it the potential to damage the catalytic converter comparatively quickly rather than just denoting a monitoring failure. So if the light has stopped blinking, the engine has stopped misfiring.

ZV

Would there be any reason why when the car is in drive, and I'm stopped, I can feel the engine kind of "hiccuping" when it's cold?

I'll manually remove the battery cable tomorrow and see if any code comes back.

 

[kornphlake]

Doubt it was this, I remember getting these changed around the 80k mark, however I don't know why I didn't replace the plugs at the same time lol.



From what I've read, these 3 coil packs control 2 cylinders each. Thankfully they're in the front so if these are the problem, I can easily change them in this weather. I don't want to go down this route if I don't have to as they are still pretty expensive and I'm planning to buy a new car this spring or summer. Is there anyway to check if it's really bad or if there is another issue?



Yes, I believe it's after 3 or so "cycles" if the ecu doesn't detect the same issue. The autozone dude wouldn't reset the code, and I just haven't had a chance to remove the battery. I'll try this weekend and see if CEL comes back.

Unless the 1zmfe engine used in the 2001 solara is different than the 1zmfe used in the 2001 sienna there are no plug wires and a coil pack for each cylinder. I'm pretty familiar with that engine in a sienna but I've never looked at a solara of the same year to compare, I can't see any reason why they'd be different though. I suspect you need to pop the hood and take a look for yourself. You come across as a real amateur not knowing something as basic as plug wires and coils, all you have to do is take off the stupid plastic cover and everything is right there on top of the engine.

You can test the primary and secondary windings in the coil with an ohm meter, you'd need a shop manual for the spec though. How friendly is your dealership service dept? One of the local dealers was cool enough to let me thumb through their FSM and take digital photos of pages I needed, the other dealership told me to pound sand.

 

[LTC8K6]

You can swap coil packs around to see if the misfire moves with the coil pack.

 

[hydroponik]

You come across as a real amateur not knowing something as basic as plug wires and coils, all you have to do is take off the stupid plastic cover and everything is right there on top of the engine.

What are you talking about? Where did I ever confuse wires and coils?

The 1mzfe in the solara utilizes 3 coil packs. The coils go into the front, and there are wires that go into the rear. Each pack controls 2 cylinders.

I was asking for help to see if there could be other reasons besides the coil going bad as I do not want to spend this cash if not necessary.

@ LTC8K6 - Thanks for your suggestion

 

[Squisher]

Yes, I believe it's after 3 or so "cycles" if the ecu doesn't detect the same issue. The autozone dude wouldn't reset the code, and I just haven't had a chance to remove the battery. I'll try this weekend and see if CEL comes back.

On my '98 F150 I believe it is 36 cycles.

 

[CraigRT]

I think your problem is already fixed, the CEL will eventually go out.
Why not for future invest in a cheap OBD code reader? They can cancel CEL's and they are like $20-50 on sale for a cheap one that will do the job.

 

[cheezmunky]

When this happened on my car it was a head gasket going. Blew about a month later. Highly unlikely that's your problem but you might want to have a leak down test done just to be sure your engine is healthy. More likely it's plugs/wires/coil packs as others have stated

 

[Gillbot]

Blinking CEL is a random misfire. Solid MIL is a "steady" misfire.

Typically it's caused by bad plugs, wires or coils. If it's a random misfire, I'd suspect coil(s).

 

[Zenmervolt]

Blinking CEL is a random misfire. Solid MIL is a "steady" misfire.

Typically it's caused by bad plugs, wires or coils. If it's a random misfire, I'd suspect coil(s).

I was pretty sure that the CEL blinked any time a severe misfire was actively occurring. That's the answer I got from several mechanics when I had the same issue with my Volvo a few years ago. According to them the CEL blinks/flashes when something is happening that can cause actual damage to the catalytic converter.

ZV

 

[Gillbot]

I was pretty sure that the CEL blinked any time a severe misfire was actively occurring. That's the answer I got from several mechanics when I had the same issue with my Volvo a few years ago. According to them the CEL blinks/flashes when something is happening that can cause actual damage to the catalytic converter.

ZV

Might be a different diagnosis per vehicle then. My service manual and scan software states blinking is a random misfire and steady MIL is a diagnosed misfire where it tells you the actual cyl misfiring.

Perhaps i'm reading too much into it also but I had to tweak the misfire tables after I installed my cam. I was getting lost of random misfires (blinking MIL) at idle and low RPM due to the increased overlap on the camshaft. When I had a bad plug on #7 though, it was a steady MIL and told me Cyl 7 misfire when I scanned it.

 

[Zenmervolt]

Might be a different diagnosis per vehicle then. My service manual and scan software states blinking is a random misfire and steady MIL is a diagnosed misfire where it tells you the actual cyl misfiring.

Perhaps i'm reading too much into it also but I had to tweak the misfire tables after I installed my cam. I was getting lost of random misfires (blinking MIL) at idle and low RPM due to the increased overlap on the camshaft. When I had a bad plug on #7 though, it was a steady MIL and told me Cyl 7 misfire when I scanned it.

Quite possible. '98 was an odd year for Volvo's monitoring systems anyway. The light did stay on solid after flashing for me, so it logged the code but flashed when the misfire was actually occurring (or when it was severe enough).

ZV

 

[Gillbot]

For a random on mine P0304, it only blinks the MIL and stores the code. It won't stay lit unless it triggers another code or a "diagnosed" misfire.